CSE391 Assignment 4- More Regular Expressions and Sed  Solved

 Task 1: Bash Shell Commands with sed​ :​
For each of the next few problems, write a command that uses sed​ (preferably with the -​ r command-line argument to enable full regular expressions) to search and replace text based on regular expressions. For some problems, you may need to combine ​grep/​ ​egrep and ​sed using ​| . Each command should use ​at most one call to ​sed,​ but you may use input/output redirection operators such as ​>, ​ ​<, and ​ ​| to combine it with other commands as needed.​

Your commands ​should not create any temporary​ files during their execution. Feel free to somewhat match your answers to the actual file you are given (e.g. only one word per line); your regexes do not have to work for a more general case). Write your commands in on the indicated lines in the ​task2.sh​ file in the ​hw7​ folder.

 

1.      Output the contents of the file ​email.txt with all spaces replaced by dashes (-).​      

2.      Josh and Zorah are debating which candy is better: kitkats or twix. We polled our friends and compiled the results in candies.txt. A quick run of ​ ​grep -i “kitkat” candies.txt | wc -l and grep -i ​ ​“twix” candies.txt | wc -l shows that 3 people prefer twix and 2 people prefer kitkats. Josh thinks this is a mistake, however, as people​           may have answered “kit kat” (with a space), “kitkats” (with an s) or “kit kats” (with both a space and an s). Write a sed command to replace all these variants with just the basic “kitkat”. You may assume that they are all lowercase.

3.      Midterm season is upon us, and things get a little rough sometimes. Write a sed command that replaces all frowny faces in ​boundless.txt with smiley faces! You may assume that all frowny faces appear with the eyes to the left of​    the mouth.

4.      Europeans format their dates differently than Americans.  Where we would write a date such as "May 12, 2010", they would write it as "12 May 2010".  Output the contents of file ​dates.txt but with all dates changed from USA format​         to European format. Don’t worry about coming up with a fancy regex to match only legal months or only legal days of the month.

5.      Convert all 10-digit phone numbers in the file phone.txt​     to 5-digit internal extension numbers.​    

       (For example, ​Abba, Cadabra    x67890 and ​ ​Timss, Aaron    x62859 .)​       

6.      Give a modified version of #3 that takes the file ​phone.txt as input and displays the phone extension first, then 3​         spaces, then the person's name.

       (For example, ​x67890   Abba, Cadabra and ​ ​x62859   Timss, Aaron .)​            

7.      Java programs can contain single-line ​// comments and multi-line ​   /*​            ... ​          ​*/ comments.  Sometimes a programmer​                uses a multi-line comment syntax, but the comment only occupies a single line.

Write a command that finds ​/* ... ​ ​*/ comments in ​ Questions.java​ ​ that occupy a single line​ and replaces them​ with a ​// comment.  For example, ​ ​/* hello there */ would become ​ ​// hello there .  (Your command​ doesn't need to modify comments where the ​/* isn't on the same line as the ​ ​*/ .  You may assume that any given line​ contains at most one comment.)

 

1  of 2 

Hints:​ The regular expression syntax hints from the previous section on ​grep also apply to ​            ​sed.  Also recall that some​      special characters must be escaped by a ​\ backslash to be used in a regex pattern.  Remember that putting a 'g' at the end​              of your pattern, such as ​s/oldpattern/newtext/g, processes all matches on a line.​      

2  of 2